In the current art of electronic control circuitry, wafers are formed of thin semiconductor slices upon which matrices of microcircuits can be fabricated, or which can be diced into individual circuit units for fabricating transistors and diodes. Since each unit contains its own microcircuit which will be placed into a combination of circuits to accomplish a desired result, it is preferred that each microcircuit be carefully tested before dicing of the semiconductor wafer in order to prevent malformed or malfunctioning circuitry from being employed.
In many cases, the microcircuits each have a plurality of input-output leads or contact points which will be utilized in the finished product. These points can also be used to test the circuitry if one probe can be accurately located on each preselected contact point. Obviously, it is quite a bit easier to test each circuit before the wafer is diced since each circuit will be properly oriented relative to the matrix pattern on the wafer. Accordingly, it has become known to put the wafer on a movable platform or worktable which may be moved relative to a plurality of identical microcircuits, the probes need be oriented relative to only one circuit and fixed in position. Then, the wafer can be moved from position to position so that each microcircuit is properly located relative to the probes for testing.
Unfortunately, the prior art devices have been rather difficult to assemble and have been unsatisfactory in use. Some prior art probes have been manufactured as a relatively flat, vertically oriented blade, a point of which can be placed in contact with an input/output connection of the microcircuit. These blades are quite stiff and must be positioned relative to the wafer with extreme accuracy. Otherwise, either the wafer or the blade will be damaged, since there is little or no flexibility in the vertically oriented blade.
Other probes have been prepared from wires which do have flexibility but which produce excessive contact resistance, can be easily bent out of a usuable position, etc.
In any case, the plurality of probes have been mounted upon a ring which is removably positioned within a bore formed in a casting or platform. Each probe is electrically connected to a high performance board which functions to connect the electrical probe leads to external circuitry, such as a computer-driven power device. These rings have to be completely removed from the casting in which they are seated in order to perform any operation upon the wiring connecting the probe to the high performance board mounted in the ring.
In other words, the construction of the prior art devices has been such that it is extremely difficult to assemble, maintain, and/or repair the probes and the wiring system connecting the probes to the high performance board mounted in the ring. Also, the probes have been highly susceptible to being damaged or damaging the circuitry by being positioned improperly.
Accordingly, it is an object of the present invention to provide an apparatus for testing the circuitry of silicone wafer devices in a manner which precludes damage to the wafers or the probes and which allows the probes to be quickly and easily serviced during construction of the ring or during maintenance. Ideally, the apparatus should be constructed in such a manner that the worktable upon which the silicone wafer is mounted can be controlled in its movement by a computer which will move the table in steps so that the individual circuits are serially presented by rows and columns to a plurality of probes mounted on the ring for testing.